Andrew
Both the Moodle logs and Grade history tables can become inflated and cause slowness on the server. Both have settings at the following url: http://yoursite//admin/settings.php?section=cleanup
Set it according to your organization's policies and needs.
Additionally, clearing the Moodle cache can help with performance.
Installing and upgrading help
Is there an audit table in Moodle?
This discussion has been locked so you can no longer reply to it.